Sense 1payback -- (financial return or reward (especially returns equal to the initial investment)) => return, issue, take, takings, proceeds, yield, payoff -- (the income or profit arising from such transactions as the sale of land or other property; "the average return was about 5%")

Sense 2vengeance, retribution, payback -- (the act of taking revenge (harming someone in retaliation for something harmful that they have done) especially in the next life; "Vengeance is mine; I will repay, saith the Lord"--Romans 12:19; "For vengeance I would do nothing. This nation is too great to look for mere revenge"--James Garfield; "he swore vengeance on the man who betrayed him"; "the swiftness of divine retribution") => retaliation, revenge -- (action taken in return for an injury or offense)

Synonyms/Hypernyms (Ordered by Estimated Frequency) of verb pay_back

2 senses of pay back

Sense 1reward, repay, pay back -- (act or give recompense in recognition of someone's behavior or actions) => act, move -- (perform an action, or work out or perform (an action); "think before you act"; "We must move quickly"; "The governor should act on the new energy bill"; "The nanny acted quickly by grabbing the toddler and covering him with a wet towel")

Sense 2pay back, pay off, get, fix -- (take vengeance on or get even; "We'll get them!"; "That'll fix him good!"; "This time I got him") => get even, get back -- (take revenge or even out a score; "I cannot accept the defeat--I want to get even")